A hypodermic needle has many applications in modem medicine. One application is to fit the hypodermic needle into a syringe and to then insert the needle into a person's body for intra-muscular, subcutaneous, or intravenous injection of medications. Another application of the hypodermic needle is to introduce a guidewire into a central vein of a person. The hypodermic needle acts as a sharp introducing instrument through which the guidewire is advanced into the vein of the patient. Following insertion of the guidewire, the needle is removed and a catheter is threaded over the guidewire and, when in place, used for diagnostic monitoring or for therapeutic procedures such as hemodialysis. Yet another application is to collect blood samples for tests using a hypodermic needle with two sharp puncturing beveled ends mounted on the barrel of a syringe. The distal puncturing end of the needle is inserted into a person's vein while an inverted rubber-capped vacuum tube is pushed into the barrel so that the other end of the needle pierces the rubber cap of the vacuum tube. Thus, a blood sample passes from the vein, through the needle, and into the vacuum tube. A fourth application of the hypodermic needle is to coaxially mount a catheter over a hypodermic needle and to puncture a vein of a person's body with the needle. Following needle puncture, the over-the-needle ("OTN") catheter is advanced into the vein, the needle is removed, and the catheter is connected to an intravenous line for fluid infusions into the vein. The foregoing applications constitute the most common applications of hypodermic needles.
A hypodermic needle entering into a patient's body is invariably contaminated by the patient's blood and body fluids. Following use of the needle, the needle presents a risk to physicians, nurses, and other health care personnel because the needle might transmit an infection or disease to such personnel if it were to accidently puncture them. Thus, health care personnel are in constant danger of contracting infections and diseases, some of which may be deadly. Other potential victims of accidental needle punctures include sanitation workers which later dispose of garbage containing the hypodermic needle. The diseases which may be transmitted by a contaminated hypodermic needle include Immune Deficiency Virus, Hepatitis, Rabies, Kure, Encephalitis, and Arbor viruses. The outcome of contracting one of these diseases is often fatal because there are no known cures for any of these diseases. Often a needle puncture in a person's skin is so trivial that it remains unrecognized until the person becomes seriously ill.
The problem of suffering accidental needle punctures is well recognized. As a result, enormous inventive effort has been devoted to concealing the sharp needle point of hypodermic needles. Despite this effort, the prevalence and magnitude of needle prick-transmitted diseases is still high, as reflected in such recent articles as "Health Care" by Helene Cooper, Wall Street Journal (Nov. 25, 1992); The G.M.P. Letter (May, 1992); Devices & Diagnostics Letter, Vol. 19, No. 19 (May 8, 1992); and FDA Medical Bulletin, Vol. 22, No. 2 (Sep. 22, 1992).
In order to avoid the transmittal of disease by needle punctures, efforts have been directed to preventing exposure of the sharp point of the hypodermic needle. One approach is to cap the needle following use. This approach, however, presents a risk of danger because it involves placing the fingers directly opposite to the needle point. To help keep the fingers away from the needle point while capping the needle, needle caps provided with wide mouths or long handles have been developed by others. Examples of such needle caps are described in U.S. Pat. Nos. 4,735,617; 4,742,910; 4,747,835; 4,767,412; 4,850,976; 4,852,584; 4,892,525; 4,906,235; 4,919,656; 4,928,824; 4,958,622; 5,066,279; 5,190,532; and 5,195,982. While the foregoing needle caps reduce the risk of suffering a needle prick, this approach still requires a person to place his/her fingers near the needle and such finger placement is an active invitation to a needle prick. It cannot be over emphasized that even a single contaminated needle prick is unacceptable.
Another approach to concealing hypodermic needles following use is to provide safe disposal containers as described in U.S. Pat. Nos. 4,746,017; 4,828,107; 4,903,832; 4,994,044; 5,024,326; and 5,067,949. Such safety containers, however, do not solve the problem because needle pricks can and do occur even before the hypodermic needles reach their final disposal destination in the safety containers.